Process for obtaining multiple photographic positive images by diffusiontransfer



3,174,858 PROCESS FOR OBTAINING MULTWLE PHQTU- GRAPHIC PQSITIVE KMAGESBY DIFFUSIDN- TRANSFER Albert Erniel Van Hoof, Berchem-Antwerp, and RenMaurice Hart and Jozef Frans Willems, Wiirijk-Antwerp, Belgium,assignors to Gevaert Photo-Producten N.V., Mortsel-Antwerp, Belgium, aBelgian company No Drawing. Filed Sept. 23, 1960, Ser. No. 57,902 Claimspriority, application Netherlands, Sept. 24, 1959, 243,371 6 Claims.(Cl. 96-29) The present invention relates to the manufacture of a numberof images by starting from one same negative according to the silvercomplex diffusion-transfer process.

According to the general principle of the diffusiontransfer processdescribed in U.S. Patent 2,352,014 and in Photography, Its Materials andProcesses" by C. B. Neblette, th edition, pages 234-244, an image-wiseexposed photographic silver halide emulsion layer (negative) is broughtinto contact with another non-light-sensitive receiving layer(positive), containing development nuclei, and developed in a developercontaining a solvent for the silver halide. During the formation of theimage in the emulsion layer sufiicient amounts of silver halide arecomplexed on the non-exposed parts of the negative which bydiffusion-transfer in the non-light-sensitive receiving layer form apositive thanks to the reducing action of the developer which iscatalyzed by the development nuclei present in the receiving layer.

The meaning of the terms negative and positive as used in thisdescription is relative; if the emulsion layer is exposed to a negativeimage, a direct negative will be produced in the reception layer; if theemulsion layer is exposed to a positive image a direct positive will beobtained in the reception layer.

This principle of diffusion-transfer process is applied in many ofiicesfor quickly printing letters, documents and drawings. In general, onlyone usable positive print can be obtained with the printing apparatussuitable for this purpose, although the quantity of silver used thereforrepresents only a small part of the available amount of silver halide inthe unexposed parts of the silver halide emulsion layer, so thattheoretically there is the possibility of making several prints of onesame negative.

It is, however, necessary to obtain sometimes as quickly and asuncostfully as possible several prints of the same original. If,however, one tries to make even a second copy of the same secondnegative by bringing the latter into contact with a second receivinglayer and according to the above-described process to lead it through aspecial developing solution, a quite unsatisfactory result is attained.

Yet, it is known to make several prints by means of one same negative byusing in the developing solution a den creasing concentration of solventfor the silver halide (Sievers A. J. Phot. Soc. of America, TechnicalQuarterly, May 1955, pp. 75-76).

It has also been proposed to add to the developing bath besides thesolvent for silver halide fixing accelerators, desensitizers for thelatent image and plasticizers for gelatin (U.S. Patent 2,834,676).

All these means, however, do not satisfy and give rather faint andpoorly intense positive images whereby the number of good positiveprints is restricted to at most 4 or 5.

It is also known to make a number of positive prints with one samenegative by slowing down the complexation of the unexposed silver halideduring processing by adding to the receiving material or to the bathcompounds which slowly give halogen ions, or by causing this com Statesate plexation to proceed in the presence of an excess of alkali halide(Belgian Patent 545,312).

New has been found that according to the silver complexdiflusion-transfer process, a number of positive prints with moreintense tone can be made from one same negative by adding to one or morelayers of the receiving material water-soluble basic polymers having inthe side chain heterocyclic nuclei which in their turn contain aquaternated nitrogen atom.

Examples of such suitable polymers are e.g. poly-(lmethyl-Z-vinylpyridinium iodide), poly-(l-methyl-Z- vinyl pyridinium methyl sulphate),poly-(1-methyl-4- vinyl-pyridinium iodide), poly-(l-methyl-4-vinylpyridinium methyl sulphate), poly-(l-vinyl-3-methyl imidazolium iodide)and poly-(l-vinyl-3-methyl imidazolium methyl sulphate).

The compounds used according to the present invention can beincorporated into several layers of the receiving material as far,however, as their presence is compatible with the elements from whichsuch repective layers are composed. In the circumstances, they can beadded to an auxiliary layer, a baryta-layer or even to the paper itself,although preferably the applied process consists in incorporating theminto the nuclei-containing layer. It was further observed that thefavorable effect obtained with the basic polymers depends on the kind ofnuclei used.

Suitable developing nuclei which act as reducing nuclei for thecomplexed silver halide are i.a. colloidal silver and sulphur, colloidalmetal sulfide such as copper-, nickel-, tinsilver and Zinc sulfide.Other compounds do not serve as nuclei but are able to form such nucleiby interaction with the diffusing silver complexes, either by reductionsuch as in the case of stannous chloride or by the formation ofdifficultly soluble compounds with sulfides or organic compounds whicheasily split off sulphur in the form of a bivalent ion such as in thecase of thiosinamine.

in order to obtain an as high as possible covering, it is advisable toapply the addition, according to the invention, to development nucleiwhich must not be too small. This can be obtained by forming thecolloidally dispersed nuclei in a medium which contains only littleprotective colloid.

Although it cannot be explained with certainty how a more intense toneis obtained with these polymers in the receiving layer, it is supposedthat the soluble silver halide complex diffuses from the negativeemulsion layer to the positive and is precipitated therein in compactform by the basic polymer present. At the same time, the diffusionequilibrium would be shifted in favor of the positive.

A further intensification of the image tone is attained, by adding toone of the layers of the positive material minor amounts of anti-foggingagents such as phenyl mercapto tetrazole, benzotriazole, mercaptobenzotn'azole etc.

An advantage of the present invention consists therein that the usualdeveloping baths and apparatus for the silver complex diffusion transferprocess can be used Without any modification. In an apparatus containingthe usual developing solution prints can be made according to the systemof one copy per negative such as described in the U.S. Patentspecification 2,352,014 as well as a number of prints of one samenegative according to the invention.

The silver halide emulsions which are suitable for applying the newmethod comprises silver chlororomide emulsions, silver bromide emulsionscontaining silver chloride and silver chlohride emulsions which all ofthem can also contain small amounts of silver iodide. However, forobtaining a quick diffusion-transfer of the complexed silver halidepreferably emulsions are used which mainly contain silver chloride. If,however, exposure times as short as possible are wanted, it isadvantageous to use sensitive silver bromide emulsions which contain asmall amount of silver chloride.

It has further been stated that when making a number of prints the firstprint adheres sufficiently strongly to the negative. In the followingprints, however, the adhering gradually decreases, so that the lastprints are spotted by lack of intimate contact between the negative andpositive prints. The adhering between positive and negative must not beraised in such a way that both can hardly be separated from each other.*The exact strength of adhering can be obtained if to the positive and/or to the negative material, but preferably to positive and negativematerials a layer of a hydrophilic watersoluble high-molecular substanceor of a mixture of such substances is applied. These substances orcolloid binding agents can be of natural and half-synthetic, as well asof fully synthetic kind. As suitable binding agents can be used arabicgum, tragacanth gum, pectine, cellulose derivatives such as methylcellulose, hydroxyl cellulose and carboxymethyl cellulose, polyvinylalcohol, partly hydrolyzed polyvinyl esters, such as polyvinyl acetate,polyvinyl pyrrolidone, dimethylhydantoine formaldehyde resins etc.

It has also been stated that hydrophilic high-molecular substances cansuccessfully be added to the image-receiving layer which for instancecontains gelatin as binding agent in order to keep the adhering of thepositive to the negative on a favorable level. Simultaneously, thesehighmolecular substances can bring along an improvement of the intensityof the positive probably in consequence of an increased reaction powerof the nuclei-containing layer thus obtained.

In this case, the positive material can be made in a very simple waysince then only one layer must be applied to the support, eg paper.

It was observed that the tanning of the colloid layer of the positive aswell as the negative exerts an unfavorable influence on obtaining auniform and sufiiciently high density on the positive. The addition oftanning agents to colloid layers indeed reduces the permeability of thelatter and makes difiicult the diiTusion-transfer of the complexatedsilver salts of the light-sensitive layer to the receiving layer. In thecircumstances it was stated that the addition of an anti-hardening orsoftening agent to at least one of the layers of the negative or of thepositive is very favorable for obtaining prints with a higher density.

There are ditferent products which are known as softening oranti-hardening agents, such as urea, water-soluble thiocyanates,nitrates and halides such as potassium thiocyanate, potassium nitrate,sodium nitrate, potassium iodide, barium chloride, calcium chloride andmagnesium chloride, ammonium salts, sodium salicylate, formamide,dimethyl formamide, ethylene chlorohydrin, chloral hydrate andalpha-naphthalene sodium sulfonate. The best results, however, wereattained with urea. This product can be added in amounts of 5 to 80% onthe weight of binding agent present in the negative and/or of thepositive layers.

In order to give the different prints obtained according to the presentinvention a better appearance and a longer life-time compounds whichcounteract the staining of the material such as for instance organichalogen containing phosphonic acid and phosphoric acid esters describedin the Belgian Patent 580,250 can be incorporated into the positivematerial which serves for the manufacture of these prints.

The following examples illustrate the present invention withoutlimiting, however, the scope thereto.

Example 1 A light-sensitive material is prepared by coating onto Gelatin40 Colloidal zinc sulfide 0.24

Sodium thiosulfate (anhydrous) 4 Fhenyl mercapto tetrazole 0.1Polyl-vinyl-3-methyl imidazolium methyl sulphate) 0.6

Water to 1000 cm.

To this positive receiving layer a second layer is applied from a 2%aqueous solution of carboxymethylcellulose. A sheet of light-sensitivematerial is image-wise exposed and in the known way brought into contactwith a sheet of image-receiving material in the presence of a developerof the following composition:

G. Sodium sulphite (anhydrous) 65 Hydroquinone 141-phenyl-3-pyrazolidone 1 Sodium hydroxide 11 Potassium bromide 1 Waterto 1000 cm.

After 5 sec., both sheets are separated from each other whereafter thelight-sensitive sheet is brought in the same Way into contact with asecond sheet of image-receiving material and is separated againtherefrom after 5 sec. By repeating this process, 10 sharp prints can bemade from one same negative.

Example 2 A light-sensitive material is prepared as in Example 1. Animage-receiving material is prepared by coating onto a g./sq. m. paper anuclei-containing layer from a suspension such as in Example 1 whereinhowever the poly-(1-vinyl-3-methyl imidazolium methyl sulphate) isreplaced by 0.4 g. of poly-(l-methyl-4-vinyl-pyridinium methylsulphate). By further treatment as in Example 1 10 sharp prints can beobtained from one same negative.

Example 3 A light-sensitive material is prepared as in Example 1. Animage-receiving material is prepared as in Example 1 but in thenuclei-containing layer composition 0.6 g. of

poly-(1-vinyl-3-methyl imidazolium methyl sulphate) is replaced by 2.5g. of poly-(1methyl-2-vinyl pyridinium iodide). By further treatment asin Example 1, 10 sharp prints can be obtained from one same negative.

Example 4 i A light-sensitive material is prepared as in Example 1. Animage-receiving material is prepared asin Example 1, but in thenuclei-containing layer composition 0.6 g. ofpoly-(1-vinyl-B-methyI-imidazolium methyl sulphate) is replaced by 0.4g. of poly-(1-methyl-4-vinyl pyridinium iodide). By further treatment asin Example 1, 10 sharp prints can be obtained from one same negative.

We claim:

1. A process for obtaining multiple copies from an exposed silver halideemulsion layer, which comprises contacting said emulsion layer with afirst receiving layer containing development nuclei, a binding agent anda water-soluble basic polymeric quaternary salt, said polymericquaternary salt having a polyvinyl chain, each monomeric unit of whichis linked directly to a five to six-membered heterocyclic nucleuscontaining as heteroatoms only nitrogen atoms, one of saidhetero-nitrogen atoms being a quaternary nitrogen atom, in the presenceof a silver halide developer and'a silver halide solvent,

separating the layers and recontacting the silver halide emulsion layerwith another of said receiving layers in the presence of said silverhalide developer and a silver halide solvent.

2. A process for obtaining multiple copies from an exposed silver halideemulsion layer which comprises contacting said emulsion layer with afirst receiving layer containing development nuclei, a binding agent,urea and a water-soluble basic polymeric quaternary salt, said polymericquaternary salt having a polyvinyl chain, each monomeric unit of whichis linked directly to a five to six-membered heterocyclic nucleuscontaining as heteroatoms only nitrogen atoms, one of saidhetero-nitrogen atoms being a quaternary nitrogen atom, in the presenceof a silver halide developer and a silver halide solvent, separating thelayers and recontacting the silver halide emulsion layer with another ofsaid receiving layers in the presence of said silver halide developerand a silver halide solvent.

3. The process of claim 1 wherein said receiving layer contains about580% by weight of said binding agent of a softening agent for saidbinding agent.

4. The process of claim 1 wherein at least one of said emulsion layerand said receiving layers bears a superposed layer of a water-solublehigh molecular weight hydrophilic colloid.

5. The process of claim 1 wherein said emulsion layer contains a bindingagent and about 580% by weight of said binding agent of a softeningagent for said binding agent.

6. The process of claim 1 wherein said heterocyclic nucleus is selectedfrom the group consisting of pyridinium and imidazolium nuclei.

References Cited in the file of this patent UNITED STATES PATENTS2,484,420 Minsk et a1. Oct. 11, 1949 2,834,676 Stanley et al May 13,1958 2,884,057 Wilson et a1 Apr. 28, 1959 2,983,606 Rogers May 9, 19613,017,270 Tregillus Ian. 16, 1962 3,075,841 Lehman et al Jan. 29, 1963FOREIGN PATENTS 1,166,232 France Nov. 4, 1958 OTHER REFERENCESGlafkides: Photographic Chemistry, Fountain Press, London (1958), pp.-157.

1. A PROCESS FOR OBTAINING MULTIPLE COPIES FROM AN EXPOSED SILVER HALIDEEMULSION LAYER, WHICH COMPRISES CONTACTING SAID EMULSION LAYER WITH AFIRST RECEIVING LAYER CONTAINING DEVELOPMENT NUCLEI, B BINDING AGENT ANDA WATER-SOLUBLE BASIC POLYMERIC QUATERNARY SALT, SAID POLYMERICQUATERNARY SALT HAVING A POLYVINYL CHAIN, EACH MONOMERIC UNIT OF WHICHIS LINKED DIRECTLY TO A FIVE TO SIX-MEMBERED HETEROCYCLIC NUCLEUSCONTAINING AS HETEROATOMS ONLY NITROGEN ATOMS, ONE OF SAIDHETERO-NITROGEN ATOMS BEING A QUATERNARY NITROGEN ATOM, IN THE PRESENCEOF A SILVER HALIDE DEVELOPER AND A SILVER HALIDE SOLVENT, SEPARATING THELAYERS AND RECONTACTING THE SILVER HALIDE EMULSION LAYER WITH ANOTHER OFSAID RECEIVIG LAYERS IN THE PRESENCE OF SAID SILVER HALIDE DEVELOPER ANDA SILVER HALIDE SOLVENT.